PurposeThis study explored the relationship between sociodemographic factors and injection utilization in South Korea. MethodsWe conducted a retrospective cross-sectional analysis using 2009 prescription claims for Korean National Health Insurance beneficiaries. We analyzed the utilization, costs, and proportion of injections in the insured market for oral-injection dual-dose-form ingredients (DFIs). We included outpatients who were prescribed DFIs with no age limits. Descriptive analysis and multivariate logistic regression were performed to evaluate the predictive factors of injection use. ResultsInjections accounted for about 5% of outpatient utilization and costs of the study drugs. The odds of having injections were 1.3-1.6 times higher among those patients who are 70years and older compared with those in the 20s, in smaller-sized hospitals and clinics than that in larger, and among medical institutions in rural areas than those in the capital area. The odds of having injections were increased stepwise for the age groups of 30-69years. Injections were more likely to be prescribed for systematic hormonal preparations and drugs for the musculoskeletal system. ConclusionsThe use of injections was higher among older groups, among smaller medical institutions, and among institutions in rural areas in Korean outpatient care. The difference between prescribing defined daily doses and prescribing rate for injections of the audit reports implies that Korean doctors prescribed injections often, but small doses for momentary effects in outpatient settings. Further studies are required to uncover the underlying causes of the high prevalence of injection use in older or rural populations and smaller institutions. Copyright (c) 2012 John Wiley & Sons, Ltd.